Fuel nozzles are used in combustors of gas turbines engines to atomize fuel for combustion purposes. One known method of atomization involves filming the fuel. The fuel is swirled generating a thin film near the discharge with some atomizing as the fuel is discharged, but most occurring because of the interface with high velocity air.
U.S. Pat. No. 4,609,150 issued to Pane et al shows a fuel nozzle swirling fuel and air for combustion. A plurality of circumferentially spaced orifices deliver fuel in a swirling manner to an annular chamber. The annular chamber supplies a frusto conical annular flow path of decreasing radius to an annular discharge. Swirling air atomizes the filmed fuel and serves as combustion supporting air.
Uniform mixing of fuel and air around the periphery of the nozzle is important to avoid local smoking as well as hot or cold streaks in the gaseous effluent and it follows that uniform delivery of fuel around the periphery is important.
The plurality of orifices described in U.S. Pat. No. 4,609,150 produces a plurality of concentrated flow areas within the fuel stream. Possible plugging of the orifices dictates a minimum orifice size. Also, the smaller the size of an orifice the greater the variation of its flow characteristic with variations in diameter caused by manufacturing tolerances. Accordingly, a very large number of small orifices cannot be used. The number of orifices which can be used is therefore limited and the spacing between the orifices is greater than would be desired for uniform distribution purposes.
The use of an annular restriction alone to distribute the flow suffers from significant maldistribution with eccentricity of the components forming the annulus.